Planetary transmissions employ a plurality of planetary gearsets and a plurality of torque-transmitting mechanisms. The torque-transmitting mechanisms are generally fluid-operated friction discs or band-type arrangements. More commonly, they are termed clutches and brakes or reaction clutches. It is common to refer to a disc-type brake as a reaction clutch in the engineering field.
The positioning of the torque-transmitting mechanisms within the transmission arrangement is an important consideration for the overall operation and compactness of a planetary transmission. Planetary transmissions generally have a hydrodynamic drive mechanism, such as a torque converter. However, it is also known that a friction device might be used as a starting element for a power transmission. In such instances, at least one of the torque-transmitting mechanisms is engaged during launch of the vehicle in either a forward or reverse operation.